HVAC Control in the New Millennium.pdf - HVAC.Amickracing

HVAC Control in the New MillenniumNetworking can streamline the control of systems that are inherentlyslow or fragile and automate these systems for higher integrity. Itis proven that networks do generate cost-effective benefits, create significanteconomies of scale, boost productivity and create unanticipated andimaginative results. Such systems have generated information that hasbeen applied to pare costs, simplify excessive or expensive procedures,locate cost variances and reduce inventories and stocks.The control network must be segmented and protected from businesstraffic to ensure the required reliability and determinism. Simplyseparating control and business networks with a bridge, or even an NTserver, is rarely sufficient. An incorrectly configured Windows workstationcan generate high levels of broadcast packets that can affect thesample time. Security breaches through the control network can alsocause problems.DDE/OLE LinkingDynamic Data Exchange (DDE) was designed as an MS Windowstool for linking data within a single PC, but many software vendorshave created extensions for full network DDE data access and linkage.This includes network data and data accessible through phone connections,remote sites and enterprise-wide networks.Object Linking and Embedding (OLE) provides a means to linkdata cells and the latest versions of entire documents, images, video andsounds. The availability and prominence of interconnectivity,interoperability and the development of user-level tools increases theimportance of existing networks.Ethernet TrendsThe future of Ethernet is strong and it will not merely be bypassedby technological changes. Other network schemes like Carrier Sense MultipleAccess with Collision Detection (CSMA/CD) networks can providebetter response times, throughputs and lower overhead, but this is offsetby the consistency and predictability of token protocols such as Ethernet.Ethernet was originally thought to reach its peak in about 1990 andbecome obsolescent by 2003. However, this is one network technologythat has blossomed and continues to gather momentum past its plannedhalf-life.©2001 by The Fairmont Press, Inc. All rights reserved.